Growth of Textured Adenine Thin Films to Exhibit only Chiral Faces

Tailoring on-surface supramolecular architectures based on adenine directed self-assembly

From an interplay of high-resolution scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations we demonstrate that by delicately choosing the parent molecule (adenine) we are able to tune the self-assembled nanostructures of adenine derivatives which are directed by the specific intermolecular interactions provided by the adenine moiety.

Onset of chiral adenine surface growth

The structure and stability of adenine crystals and thin layers has been studied by using scanning tunneling microscopy, X-ray diffraction, and density functional theory calculations. We have found that adenine crystals can be grown in two phases that are energetically quasi-degenerate, the structure of which can be described as a pile-up of 2D adenine planes. In each plane, the structure can be described as an aggregation of adenine dimers. Under certain conditions, kinetic effects can favor the growth of the less stable phase. These results have been used to understand the growth of adenine thin films on gold under ultra-high vacuum conditions. We have found that the grown phase corresponds to the α-phase, which is composed of stacked prochiral planes. In this way, the adenine nanocrystals exhibit a surface that is enantiopure. These results could open new insight into the applications of adenine in biological, medical, and enantioselective or pharmaceutical fields.